Firing apparatus for gun perforators



Oct. 5, 1943. J. c. STICK; JR

FIRING APPARATUS FOR GUN PERFORATORS Filed Aug. 14, 1942 INVENTOR Jar/xv C STICK. Je.

BY ATTORNEY Patented Oct. 5, 1943 FIRING APPARATUS FOR GUN PERFORATORS John C. Stick, Jr.. South Pasadena, Calif., assignor to Lane-Wells Company, Los Angeles, Calif., a corporation of Delaware Application August 14, 1942, Serial No. 454,863

9 Claims.

My invention relates to firing apparatus for gun perforators; that is, to remotely controlled apparatus adapted to be assembled as a unit with a gun perforator and lowered by a cable into a well bore for the purpose of causing the gun perforator to discharge bullets through a surrounding casing and provide openings for the entrance of oil. Among the objects of my invention are:

First, to provide a firing apparatus for gun perforators which permits the use of a conductor cable having a comparatively high resistance and low current-carrying capacity whereby a cable of small diameter having a small conductor or a conductor having relatively high resistance, such as a steel conductor in place of the usual copper conductor, may be utilized to suspend and furnish electrical energy for operation of the gun;

Second. to provide a firing apparatus for a gun perforator which may employ the apparatus no used in the present conventional gun perforator,

, namely, a sequencing switch or controller, so that no changes are necessary in the arrangement of the gun itself and its controller in order to utilize the advantages of my firing apparatus, the apparatus being arranged as a unit to be interposed between the controller and supply cable;

Third, to provide a firing apparatus for gun perforators which is so interconnected with the controller and gun units of the gun perforator that the gun perforator may be caused to fire one shot, and one shot only, each time a trigger switch at the surface is closed, reducing to a minimum any possibility that the gun might machine gun or fire several shots when only one shot is intended;

Fourth, to provide a firing apparatus for gun perforators which is inherently safe in that a condenser or condensers are used to store the energy necessary to operate the gun, which condensers are so arranged that they loose their charges within a short time after the current supply is out 01f, so that the whole electrical system soon becomes inert a short time after the power supply is disconnected, thereby preventing any possibility of accidental discharge of the gun either before it is lowered into the well or after it is brought to the surface; and

Fifth, to provide, in a modification, a firing apparatus of this character whereby a particularly heavy current surge may be applied to the series of electrical cartridges provided in the gun units of the gun perforator, so that although the resistances of these cartridges may vary over a wide range the current surge is large enough to ignite all of the cartridges virtually simultaneously and minimize the possibility that one cartridge might fire ahead of the others and short circuit, and thereby prevent firing of the other gun units, that is, the current surge may be large enough that all of the gun units fire within the time that would be required for a single gun unit to fire and form a short circuit.

With the above and other objects in view, as may appear hereinafter, reference is directed to the accompanying drawing, in which:

Figure 1 is a wiring diagram showing one form of my firing apparatus in conjunction with a controller and gun unit of a gun perforator;

Figure 2 is a wiring diagram of a modified form of my apparatus; and

Figure 3 is another wiring diagram of a further modified form wherein the controller is omitted and the gun units of the gun perforator are fired simultaneously.

My firing apparatus is particularly designed to fire in sequence the gun units of a gun perforator such as shown in the Johnston Patent No. 2,048,- 451 or the Lane Patent No. 2,062,974, or the Yarbrough Patent No. 2,142,583. With reference to Figure 1, the gun units l are indicated diagrammatically; these comprise cartridges 2, each containing a fuse wire adapted, when heated, to ignite the powder charge and drive a bullet 3 from the barrel (not shown) of the gun unit. Each of the cartridges is grounded to the body of the gun perforator and is connected by an individual wire to a contact 4 of a sequencing switch 5, there being a contact for each cartridge. The grounded side of the circuit may be through the bullets to the gun body as shown 'in the Johnston or Lane patents, or the bullets may be insulated and connected individually to the lead wires, in which case the inner ends of the cartridges are grounded as shown in the Yarbrough patent. A sweeper arm 6 is adapted to engage the contacts 4 in sequence. The sweeper arm is connected by a shaft I to a ratchet 8 which is actuated by a pawl 9 carried on a suitable armature I0 coacting with a solenoid ll. One end of the solenoid coil is grounded through a resistor l2 to the body of the gun perforator, while the other end is connected to a supply lead l3. Also connected to the supply lead is a, switch M which is in series with the sweeper arm 6 of the sequencing switch.

The switch I4 is adapted to be engaged by a lug is provided with a. weight-carrying sheath la. The cable may be of the character disclosed in Patent 2,043,401. However, it is contemplated (as will be brought out in more detail hereinafter) that cable of materially higher resistance than the type shown in the above mentioned patent may be employed.

A resistor 20 and relay coil 2| of the relay I6 is connected between the conductor l1 and the rounded side of the circuit represented by the body of the gun perforator and the sheath of the cable. Also connected across the circuit between the conductor l1 and the ground is a condenser 22 of suflicient capacity to provide the energy for the operation of the solenoid II and the gun units I, as will be described hereinafter.

The cable I8 is suitably wound upon a hoisting drum (not shown) and is connected at its upper end to a source of direct current in which is interposed a firing or trigger switch 23.

Operation of the apparatus as represented in Figure 1 is as follows: When the firing switch 23 is closed the condenser 22 begins to charge. Initially the voltage differential across the condenser is zero. This voltage differential gradually increases. increasing .the voltage across the relay coil until the relay coil causes the contacts I to close, thereupon the charge of the condenser is drained rapidly through the solenoid l I to actuate the sequencing switch and close contact It so as to complete a circuit to the corresponding gun unit. Operation of the circuit may be determoned by an ammeter 24 located adjacent the firing switch. The drain on the condenser through the solenoid ll of course soon lowers the voltage across the relay coil 2| to the point that the contact l5 opens and the condenser begins to charge again. At this point, however. if it is desired to fire only one shot each time the firing switch is closed the operator releases immediately the firin switch: on the other hand if it is desired to fire the gun unit at automatically spaced intervals the firing switch may merely be held down. and as soon as the condenser has again charged sufiiciently the relay and sequencing switch are a ain caused to operate and the next gun unit fired.

The length of time required to charge the condenser depends upon:

1. The voltage of the power supply.

2. The size of the condenser.

3. The resistance of the cable.

The voltage that may be applied is limited by the insulation of the cable to about 150 to 200 volts. The condenser size is fixed and is deter mined by the amount of power required to operate the electrical parts of the gun perforator. Therefore, for a given condenser and a given voltage supply, the charging rate of the condenser will de end upon the resistance of the cable; the higher the resistance the longer the charging time.

Actual tests have indicated that a condenser having 350 microfarads capacity causes the relay to trigger or close its contacts when the voltage difierentialreaches approximately 100 volts and has sufficient power to insure operation of the sequencing switch and discharge of a gun unit. With a conventional cable having a copper conductor of approximately 4.5 ohms per thousand.

feet the gun discharges almost simultaneously with the closing of the firing switch. However, the interval between closure of the firing switch and discharge of the gun is increased as the resistance of the cable increases. It is feasible to have several thousand ohms resistance in the cable and still insure completely satisfactory operation of the gun. This is of primary importance for the reason that an all steel cable may be employed, that is, one with a steel core or conductor in place of a copper conductor. Furthermore, the size of the conductor may be reduced from the conventional 17 gauge copper conductor down to as low or lower than a 14 gauge steel conductor (equivalent in diameter to about gauge copper wire) This not only permits substitution of the less strategic steel wire for the more strategic copper wire, but also permits the -reduction in over-all diameter of the cable. Inasmuch as the present standard cable weighs approximately 330 pounds per thousand feet and it is customary to carry as much as 12,000 feet of cable, a tremendous saving in weight of the hoisting equipment is possible. It is possible to reduce the present weight of the cable from one-fourth to one-third and still provide suflicient tensile strength to carry the load of the gun. Furthermore, by the use of a steel core not only is the tensile strength of such core added to the total strength of the cable but also the steel core has materially more resiliency than the copper core, so that severe strains on the cable have less tendency to damage the core.

Reference is now directed to Figure 2: While with proper skill on the part of the operator the arrangement in Figure 1 may be employed to fire one shot at a time, at the will of the operator, the arrangement in Figure 2 is more foolproof in that regardless of the length of time the firing switch is held closed the cycle of operation will not repeat. In this circuit a relay 3| is substituted for the relay l6 and is equipped with two contacts 32 and 33 connected with the conductor ll of the cable. Contact 32 is a double throw contact which engages either a solenoid contact 34 or a firing condenser contact 35. Thsolenoid contact 34 is connected to a supply-HM which is connected through the solenoid II and resistor l2 to ground. The switch I4 is connected to the firing condenser contact 35 as is also a firing condenser 36, the remaining side of which is connected to ground, so that the firing condenser 36 is across the gun unit switch l4 and sequencer switch. The relay coil 31 of the relay 3| is connected through the resistor 20 to the conductor I! as in the first described structure, but is also connected to the conductor I! through a resistor 38 and a contact 39 which coact with the second of the two supply contacts, namely, contact 33. As in the first described structure, a condenser 22 is placed across the circuit between the conductor I1 and ground.

Operation of the circuit shown in Figure 2 is as follows: When the firing switch 23 is closed the relay contacts are in the position shown and both condenser Hand 36 are charged by the supply current, it being noted that contact 32 is in engagement with the firing condenser contact 35 so that both condensers are across the circuit between the conductor l1 and ground. When condenser 22 has charged sufliciently relay 3! operates, completing a circuit between contacts 32 and 34 to the solenoid and opening the connection between the firing condenser 36 and the conductor IT. The condenser 22 energizes the solenoid ll, causing its'armature to close switch 14 so as to place the firing condenser 36 across the sequencer switch and gun unit selected thereby. The entire energy of the fully charged firing condenser 36 is therefore utilized to fire to incandescence virtually simultaneously,

the gun unit while condenser 22 is utilized only to operate the relay and solenoid, whereas in the first described structure the condenser 22 is partially discharged before it is connected to the gun unit. Also, it should be noted that when the relay 3| is operated the resistance in series with the coil of the relay is reduced, for both resistances 20 and 38 connect the relay coil to the conductor II. This relay may be designed to operate on a comparatively small amount of current, such as 5 to milliamperes, so that even though the cable isof a high resistance suflicient current is always available through the lowered resistance obtained when the relay is energized to maintain the relay ener-. gized after having been operated by the condenser charge until the firing switch is again opened. Consequently, the firing switch may be closed and held closed, and the firing apparatus will proceed through only one cycle of operation and fire only a single gun unit.

Reference is now directed to Figure 3: The circuit here shown is designed to fire all the shots of a gun perforator simultaneously, particularly to supply suflicient instantaneous power to insure simultaneous firing although the cur rent available through the conductor is severely limited. In this arrangement the sequencing switch is entirely eliminated. The several gun units are connected in parallel between ground and a common supply lead H which is connected to one of the contacts 42 of a relay 43, the relay coil of which is connected to ground and through a resistor 44 to the conductor l1, similar to the relay l6. Condensers 45, 46, etc., are connected between the conductor I! and the ground to provide the current necessary to discharge all of the gun units.

Operation is as follows: When the triggering switch or firing switch 23 is closed the condensers charge at a rate depending upon the current supplied through the cable, and when a predetermined charge is reached the relay is energized, closing the switch common to the several gun units, whereupon they discharge simultaneously. In this connection, it should be noted that a relatively large, sudden surge of electrical energy is required in order to insure that all of the gun units may fire. If the current were built up gradually one of the gun units might easily fire ahead of the others for it is impossible to, insure that the resistances of the electrical elements in the several gun units are equal. Should one of the gun units fire and short the circuit at that point, then the remaining gun units would not fire. However, by providing an ample, sudden current surge, made possible by the condensers in close proximity to the gun perforator and hence very low inductance in the circuit, all of the filaments in the cartridges heat at least sufiiciently that a short can not occur before all of the units have discharged. It is of course necessary that the switch 42, as well as other leads in the circuit, be capable of passing the full current necessary. It should be noted that while only a few gun units are shown, in actual practice as many as two dozen or more units may be fired at once by the use of the condensers and relay with ample current-carrying capacity in the relay switch. This is true although the cable may be capable of passing only a few milliamperes since it is possible to charge the condensers to a point where its discharge current will amount to several amperes, or several hundred amperes, if such excessively large current were required. In contrast with this, a conventional gun perforator, even though suspended by a cable having relatively low resistance, capable of passing as much as an ampere, will fire only comparatively few cartridges as one of the cartridges is likely to short before the others have been heated sumcient to ignite the powder.

Various changes and alternate arrangements may be made within the scope of the appended claims, in which it is my intention to claim all novelty inherent in the invention.

I claim:

1. The combination with a weight-supporting cable having a conductor. of only nominalcurrent-carrying ability and an electrically fired gun perforator adapted to be moved in a well bore by said cable and requiring for its operation cur rent in excess of that available through said conductor, of a firing apparatus comprising: a condenser suspended from said cable as a unit with said gun perforator and adapted to be charged by current through said conductor; a relay including contacts adapted to complete a circuit across said condenser through electrical parts of said gun, said condenser having surficient capacity to supply the current required by said electrical parts, and a relay coil responsive to a predetermined voltage differential across said condenser to close said contacts and permit discharge of said condenser through said electrical parts.

2. The combination with a weight-supporting cable having a conductor of only nominal current-carrying ability and an electrically fired gun perforator adapted to be moved in a well bore by said cable and requiring for its operation current in excess of that available through said conductor, of a firing apparatus comprising: a condenser and a relay suspended from said cable as a unit with said gun perforator and both electrically positioned across the supply circuit through said cable, the electrical parts of said gun perforator being connected across said condenser to receive the discharge therefrom, and contacts incorporated in said relay and in series with said electrical parts adapted to be closed by said relay when said condenser becomes charged.

3. The combination with a weight-supporting cable having a supply circuit including a conductor of only nominal current-carrying ability and an electrically fired gun perforator having a plurality of gun units each including an explosive cartridge containing an electric ignition wire of random resistance, said ignition wires of the several gun units being electrically connected in parallel, of a firing apparatus comprising: a condenser and relay suspended from said cable as a unit with said gun perforator and connected across the supply circuit through said cable, and said condenser adapted to be charged by current supplied therethrough; said relay including contacts adapted to connect said fuse wires simultaneously across said condenser when said relay is energized, said condenser having a capacity capable of producing a current surge materially in excess of the steady current required to fuse said ignition wires, whereby said ignition wires, although having random resistances, fuse virtually simultaneously.

4. The combination with a cable having a weight-carrying grounded sheath and a single insulated conductor of nominal current-carrying ability and an electrical gun perforator having a plurality of gun units, each with an electrically ignited cartridge, of a firing apparatus comprising: a switch adapted to connect said gun units in sequence to a source; a condenser constituting the energy source for said gun units; means for charging said condenser through said cable; and relay switch means between said condenser and gun units adapted to be closed when said condenser is charged to cause a discharge through the sequencing switch and gun unit selected thereby.

5. The combination with a cable having a weight-carrying grounded sheath and a single insulated conductor of nominal current-carrying ability and an electrical gun perfoi'ator having a plurality of gun units, each with an electrically ignited cartridge, of a firing apparatus comprising: a switch adapted to connect said gun units in sequence to a source, said sequencing switch including a solenoid coil; a condenser for energizing said solenoid coil; a second condenser constituting the source for the gun unit selected by the sequencing switch; and means for connecting both of said condensers to said cable to receive a charging current connecting said condensers individually to said solenoid and gun unit. I

6. The combination with a cable having a weight-carrying grounded sheath and a single insulated conductor of nominal current-carrying ability and an electrical gun perforator having a plurality of gun units, each with an electrically ignited cartridge, of a firing apparatus comprising: a selector switch for connecting said firing condenser to said gun units in sequence; a control condenser for said selector switch; and a relay for connecting said condensers to said cable to receive a charging current and for connecting said selector switch to said control condenser, thereby to cause said selector switch to connect said firing condenser with the selected gun unit. 7, The combination with a limited source of electrical energy and an electrically fired gun perforator requiring for its operation current in excess of that available from said source, of a firing apparatus comprising: a condenser moun sufiicient capacity to supply the current required by said electrical parts, and a relay coil respon- .sive to a predetermined voltage differential across said condenser to close said contacts and permit discharge of said condenser through said electrical parts.

8. The combination with a limited source of electrical energy and an electrically fired gun perforator requiring for its operation current in excess of that available from said source, of a firing apparatus comprising: a condenser and relay mounted as a unit with said gun perforator and both electrically positioned across said supply, the electrical parts of said gun perforator being connected across said condenser to receive the discharge therefrom, and contacts incorporated in said relay and in series with said electrical parts adapted to be closed by said relay when said condenser becomes charged.

9. The combination with a limited source of electrical energy and an electrically fired gun perforator having a plurality of gun units, each including an explosive cartridge containing an electric ignition wire of random resistance, said ignition wires of the several gun units being electrically connected in parallel, of a'iflring apparatus comprising: a condenser and relay mount ed as a unit with said gun perforator. and connected across said source, said condenser adapted to be charged by current supplied from 'said source; said relay including contacts adapted to connect said fuse wires simultaneously across said condenser when said relay is energized, said condenser having a capacity capable of producing a current surge materially in excess of the steady current required to fuse said ignition wires, whereby said ignition wires, although having random resistances, fuse virtually simultaneously.

JOHN C. STICK, JR. 

